From mediawiki.org
Please first review the MediaWiki API and REST APIs to see if they meet your needs. These will be considerably faster than XTools and allow for asynchronous requests.

The XTools features a rich API for much of the data available through the web interface. Out of courtesy we ask you make requests synchronously – as in one full round trip – before making a new request. Please leave an informative user agent in your request so we can contact you if we need to.

Response format

All endpoints will return the requested parameters (such as project, username, etc.), the requested data, followed by the elapsed_time of how long the request took to process in seconds.

Check the examples in the documentation for the exact format of each endpoint. All data is returned as JSON, in addition to other formats as noted.

This API is not versioned. Make note of warnings in the response that will announce deprecations and future changes.

Errors and warnings

Error messages will be given error key. Flash messages may also be shown with the keys info, warning or danger. Keep an eye out for warning in particular, which will announce deprecations.

To ensure performance and stability, most endpoints related to users will return an error if the user has made an exceptionally high number of edits.